1. Field of the Invention
The present invention relates to a semiconductor device and a method for production thereof and, more particularly, to a semiconductor device containing transistors of trench gate structure and a method for production thereof.
2. Description of Related Art
There is known a technology of forming surface irregularities such as trenches in the channel region on a substrate in order to substantially expand the channel width of a transistor.
For example, there has been disclosed a semiconductor containing transistors of trench gate structure which has trenches formed on its substrate surface. See Japanese Application Publication No. Hei11(1999)-103058.
There has also been disclosed a semiconductor device or a field effect transistor which has, in the substrate of the semiconductor held between the source region and the drain region formed in the substrate of the semiconductor, a gate electrode formed in the vertical direction with respect to the surface direction of the substrate of the semiconductor, so that the channel region for current flowing between the source region and the drain region is formed along the gate electrode and in the vertical direction with respect to the surface of the substrate of the semiconductor. See Japanese Application Publication No. Hei11(1999)-150265.
In addition, there has been disclosed a semiconductor device which has a well region of high-resistance first conductivity type formed to a certain depth from the surface of semiconductor, a plurality of trenches reaching the midway from the surface of the well region, a gate insulating film formed on the surface of irregularities for the trenches to be formed, a gate electrode buried inside the trenches, a gate insulating film formed on the substrate surface in contact with the gate electrode buried inside the trenches in the irregularities region excluding the neighborhood of both ends of the trench, and a source region and a drain region which are two semiconductor layers of low-resistance second conductivity type and are formed shallower than the well region in the well region excluding the lower part of the gate insulting film. See Japanese Application Publication No. 2006-294645.